Potassium niobate deposited body and method for manufacturing the same, surface acoustic wave element, frequency filter, oscillator, electronic circuit, and electronic apparatus

ABSTRACT

A potassium niobate deposited body in accordance with an embodiment of the invention includes an R-plane sapphire substrate, and a potassium niobate layer or a potassium niobate solid solution layer formed above the R-plane sapphire substrate, wherein the potassium niobate layer or the potassium niobate solid solution layer epitaxially grows in a (100) orientation in a pseudo cubic system expression, and the potassium niobate layer or the potassium niobate solid solution layer has a (100) plane that tilts with a [ 11 - 20 ] direction vector as a rotation axis with respect to an R-plane ( 1 - 102 ) of the R-plane sapphire substrate.

The entire disclosure of Japanese Patent Application No. 2005-060915,filed Mar. 4, 2005 is expressly incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to potassium niobate deposited bodies andmethods for manufacturing the same, surface acoustic wave elements,frequency filters, oscillators, electronic circuits, and electronicapparatuses.

2. Related Art

Accompanying the considerable development in the telecommunicationsfield, the demand for surface acoustic wave elements is rapidlyexpanding. The development of surface acoustic wave elements is directedtoward achieving further miniaturization, higher efficiency and higherfrequency. In order to achieve this, higher electromechanical couplingcoefficient, more stable temperature characteristics and greater surfaceacoustic wave propagation speed are needed.

It has been found that a single crystal substrate of potassium niobate(KNbO₃) (a=0.5695 nm, b=0.3973 nm, and c=0.5721 nm; hereafter this indexexpression is followed as “orthorhombic crystal”) exhibited a largevalue of electromechanical coupling coefficient. For example, asdescribed in Jpn. J. Appl. Phys. Vol. 37 (1998) 2929, it was confirmedby experiments that a 0° Y-cut X propagation KNbO₃ single crystalsubstrate (hereafter referred to as a “0° Y—X—KNbO₃ substrate”) wouldexhibit a very large value of electromechanical coupling coefficientreaching as much as about 50%. Also, the same reference reports that theoscillation frequency of a filter using 45° to 75° rotated Y-cut Xpropagation KNbO₃ single crystal substrate (hereafter referred to as a“rotated Y—X—KNbO₃ substrate”) exhibited a zero-temperaturecharacteristic around room temperature.

In a surface acoustic wave element that uses a piezoelectric singlecrystal substrate, its electromechanical coupling coefficient,temperature coefficient, and acoustic velocity define values peculiar tothe piezoelectric material used, and are decided according to a cutangle and a propagation direction. 0° Y—X—KNbO₃ single crystalsubstrates exhibit an excellent electromechanical coupling coefficient,but do not exhibit a zero-temperature characteristic like 45° to 75°rotated Y—X—KNbO₃ substrates around room temperature. Moreover, theacoustic velocity of a 0° Y—X—KNbO₃ single crystal substrate is lowercompared to SrTiO₃ which is the same perovskite type oxide. Thus, all ofthe requirements of high electromechanical coupling coefficient,zero-temperature characteristic and high acoustic velocity cannot besatisfied by merely using a KNbO₃ single crystal substrate. Moreover, itmay be difficult to manufacture a surface acoustic wave element byforming a thin film of potassium niobate on a certain substrate having alarge area.

SUMMARY

In accordance with an aspect of the present invention, there areprovided a potassium niobate deposited body having a potassium niobatethin film, and a method for manufacturing the same.

In accordance with another aspect of the invention, a surface acousticwave element with a high electromechanical coupling coefficient isprovided.

In accordance with still another aspect of the invention, frequencyfilters, oscillators, electronic circuits, and electronic equipmentincluding the surface acoustic wave element are provided.

A potassium niobate deposited body in accordance with an embodiment ofthe invention includes:

-   -   an R-plane sapphire substrate; and    -   a potassium niobate layer or a potassium niobate solid solution        layer formed above the R-plane sapphire substrate,    -   wherein the potassium niobate layer or the potassium niobate        solid solution layer epitaxially grows in a (100) orientation in        a pseudo cubic system expression, and    -   the potassium niobate layer or the potassium niobate solid        solution layer has a (100) plane that tilts with a [11-20]        direction vector as a rotation axis with respect to an R-plane        (1-102) of the R-plane sapphire substrate.

According to the potassium niobate deposited body described above, the(100) plane of the potassium niobate layer or the potassium niobatesolid solution layer tilts with a [11-20] direction vector as a rotationaxis with respect to the R-plane (1-102) of the R-plane sapphiresubstrate. By using the above-described potassium niobate deposited bodyhaving the potassium niobate layer or potassium niobate solid solutionlayer described above, a surface acoustic wave element having a highelectromechanical coupling coefficient can be obtained.

It is noted that, in the invention, forming another specific member(hereafter referred to as “B”) above a specific member (hereafterreferred to as “A”) includes a case of forming “B” directly on “A,” anda case of forming “B” over “A” through another member on “A.” Also, inthe invention, “B” formed above “A” includes “B” formed directly on “A,”and “B” formed above “A” through another member on “A.”

In the potassium niobate deposited body in accordance with an aspect ofthe invention, an angle defined between the (100) plane of the potassiumniobate layer or the potassium niobate solid solution layer and theR-plane (1-102) of the R-plane sapphire substrate may be one degree orgreater but 15 degrees or smaller.

In the potassium niobate deposited body in accordance with an aspect ofthe invention,

the potassium niobate layer may include a domain that epitaxially growsin a b-axis orientation, when a lattice constant of orthorhombicpotassium niobate is 2^(1/2) b<a<c, and a c-axis is a polarization axis,and

the b-axis may tilt with a [11-20] direction vector as a rotation axiswith respect to the R-plane (1-102) of the R-plane sapphire substrate.

In the potassium niobate deposited body in accordance with an aspect ofthe invention, an angle defined between the b-axis and the R-plane(1-102) of the R-plane sapphire substrate may be one degree or greaterbut 15 degrees or smaller.

The potassium niobate deposited body in accordance with an aspect of theinvention may include a buffer layer formed above the R-plane sapphiresubstrate, wherein the potassium niobate layer or the potassium niobatesolid solution layer may be formed above the buffer layer.

In the potassium niobate deposited body in accordance with an aspect ofthe invention, the buffer layer may epitaxially grow in a cubic (100)orientation, and a (100) plane of the buffer layer tilts with a [11-20]direction vector as a rotation axis with respect to the R-plane (1-102)of the R-plane sapphire substrate.

A potassium niobate deposited body in accordance with another embodimentof the invention includes:

-   -   an R-plane sapphire substrate;    -   a buffer layer formed above the R-plane sapphire substrate; and    -   a potassium niobate layer or a potassium niobate solid solution        layer formed above the buffer layer,    -   wherein the buffer layer epitaxially grows in a cubic (100)        orientation, and a (100) plane of the buffer layer tilts with a        [11-20] direction vector as a rotation axis with respect to an        R-plane (1-102) of the R-plane sapphire substrate.

In the potassium niobate deposited body in accordance with an aspect ofthe invention, an angle defined between the (100) plane of the bufferlayer and the R-plane (1-102) of the R-plane sapphire substrate may beone degree or greater but 15 degrees or smaller.

In the potassium niobate deposited body in accordance with an aspect ofthe invention, the buffer layer may consist of a metal oxide having arock salt structure.

In the potassium niobate deposited body in accordance with an aspect ofthe invention, the metal oxide may be magnesium oxide.

In the potassium niobate deposited body in accordance with an aspect ofthe invention, the potassium niobate solid solution layer may be a solidsolution that is expressed by K_(1-x)Na_(x)Nb_(1-y)Ta_(y)O₃ (0<x<1,0<y<1).

A method for manufacturing a potassium niobate deposited body inaccordance with still another embodiment of the invention includes:forming above an R-plane sapphire substrate a potassium niobate layer ora potassium niobate solid solution layer that epitaxially grows in a(100) orientation in a pseudo cubic system expression, wherein a (100)plane of the potassium niobate layer or the potassium niobate solidsolution layer is formed to tilt with a [11-20] direction vector as arotation axis with respect to an R-plane (1-102) of the R-plane sapphiresubstrate.

A method for manufacturing a potassium niobate deposited body inaccordance with an embodiment of the invention includes: forming abuffer layer that epitaxially grows in a cubic (100) orientation abovean R-plane sapphire substrate, and forming a potassium niobate layer ora potassium niobate solid solution layer above the buffer layer, whereina (100) plane of the buffer layer is formed to tilt with a [11-20]direction vector as a rotation axis with respect to an R-plane (1-102)of the R-plane sapphire substrate.

A surface acoustic wave element in accordance with an embodiment of theinvention includes the potassium niobate deposited body described above.

A frequency filter in accordance with an embodiment of the inventionincludes the surface acoustic wave element described above.

An oscillator in accordance with an embodiment of the invention includesthe surface acoustic wave element described above.

An electronic circuit in accordance with an embodiment of the inventionincludes at least one of the frequency filter and the oscillatordescribed above.

An electronic apparatus in accordance with an embodiment of theinvention includes the electronic circuit described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a potassiumniobate deposited body in accordance with a first embodiment of theinvention.

FIG. 2 is a view schematically showing a hexagonal sapphire crystal.

FIG. 3 is a view schematically showing a tilt between a buffer layer anda potassium niobate layer.

FIG. 4 is an X-ray diffraction diagram of a potassium niobate layer inaccordance with a first experimental example.

FIG. 5 is a RHEED pattern of a sapphire substrate in accordance with asecond experimental example.

FIG. 6 is a RHEED pattern of a buffer layer in accordance with thesecond experimental example.

FIG. 7 is a 2θ-θ scanning X-ray diffraction diagram of the buffer layerin accordance with the second experimental example.

FIG. 8 is a ω scanning X-ray diffraction diagram of the buffer layer inaccordance with the second experimental example.

FIG. 9 is a ω scanning X-ray diffraction diagram of the buffer layer inaccordance with the second experimental example.

FIG. 10 is a RHEED pattern of a KNbO₃ layer in accordance with thesecond experimental example.

FIG. 11 is a 2θ-θ scanning X-ray diffraction diagram of the KNbO₃ layerin accordance with the second experimental example.

FIG. 12 is a ω scanning X-ray diffraction diagram of the KNbO₃ layer inaccordance with the second experimental example.

FIG. 13 is a ω scanning X-ray diffraction diagram of the KNbO₃ layer inaccordance with the second experimental example.

FIG. 14 is an X-ray diffraction pole figure of the sapphire substrate inaccordance with the second experimental example.

FIG. 15 is an X-ray diffraction pole figure of the buffer layer inaccordance with the second experimental example.

FIG. 16 is an X-ray diffraction pole figure of KNbO₃ in accordance withthe second experimental example.

FIG. 17 is a diagram showing Raman scattering spectra of KNbO₃ inaccordance with the second experimental example.

FIG. 18 is a diagram showing Raman scattering spectra of KNbO₃ inaccordance with the second experimental example.

FIG. 19 is a cross-sectional view of a surface acoustic wave element inaccordance with the second embodiment.

FIG. 20 is a perspective view of a frequency filter in accordance with athird embodiment of the invention.

FIG. 21 is a perspective view of an oscillator in accordance with afourth embodiment of the invention.

FIG. 22 is a schematic view of an example in which the oscillator inaccordance with the fourth embodiment is applied to a VCSO.

FIG. 23 is a schematic view of the example in which the oscillator inaccordance with the fourth embodiment is applied to a VCSO.

FIG. 24 is a block diagram of the basic structure of a PLL circuit.

FIG. 25 is a block diagram showing the structure of an electroniccircuit in accordance with a fifth embodiment of the present invention.

FIG. 26 is a view showing a communications system that uses areader/writer in accordance with the fifth embodiment of the presentinvention.

FIG. 27 is a schematic block diagram of the communications system shownin FIG. 26.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Preferred embodiments of the present invention are described below withreference to the accompanying drawings.

1. First Embodiment

1.1. FIG. 1 is a cross-sectional view schematically showing a potassiumniobate deposited body 100 in accordance with an embodiment of theinvention. As shown in FIG. 1, the potassium niobate deposited body 100in accordance with the present embodiment includes a substrate 11, abuffer layer 12 formed on the substrate 11, and a potassium niobatelayer 13 formed on the buffer layer 12.

An R-plane sapphire substrate may be used as the substrate 11. The useof an R-plane sapphire substrate is desirable because the buffer layer12 and the potassium niobate layer 13 can be epitaxially grown thereon,a large surface area substrate can be obtained at a low price, and theR-plane sapphire substrate has a tolerance to etchant and can be usedrepeatedly.

As the buffer layer 12, for example, a metal oxide having a rock saltstructure can be used. For example, magnesium oxide (MgO) may be used asthe metal oxide having a rock salt structure. The buffer layer 12 shallbe described in detail below.

The potassium niobate layer 13 has single crystal potassium niobate orpolycrystal crystal potassium niobate. The thickness of the potassiumniobate layer 13 can be appropriately selected according to devices towhich the potassium niobate deposited body is applied without anyparticular limitation, but for example, may be 100 nm or greater but 10μm or less. The potassium niobate layer 13 shall be described in detailbelow.

In the present embodiment, instead of the potassium niobate layer 13described above, it may be a layer of potassium niobate solid solutionin which a part of niobium and potassium of potassium niobate isreplaced with other elements. As the potassium niobate solid solution,for example, a potassium sodium niobate tantalate solid solutionexpressed by K_(1-x)Na_(x)Nb_(1-y)Ta_(y)O₃ (0<x<1, 0<y<1) can beenumerated. The same similarly applies to embodiments to be describedbelow.

1.2. Next, a method for manufacturing a potassium niobate deposited body100 is described.

(1) First, as shown in FIG. 1, a substrate composed of an R-planesapphire substrate (hereafter also referred to as an “R-plane sapphiresubstrate”) 11 is prepared. The R-plane sapphire substrate 11 has beendegreased and washed beforehand. Degreasing and washing can be conductedby soaking the R-plane sapphire substrate in an organic solvent with anultrasonic washing machine. The organic solvent is not particularlylimited, but may be a mixed solution of ethyl alcohol and acetone.

(2) Next, a buffer layer 12 that consists of MgO is formed on theR-plane sapphire substrate 11 by a laser ablation method, as shown inFIG. 1.

More specifically, after the R-plane sapphire substrate 11 that has beendegreased and washed is loaded onto a substrate holder, it is introducedtogether with the substrate holder in a vacuum apparatus whose backpressure at room temperature is 1×10⁻⁸ Torr. Next, oxygen gas isintroduced such that the oxygen partial pressure becomes 5×10⁻⁵ Torr,for example, and then the substrate is heated to elevate its temperatureup to 400° C. at a rate of 20° C./minute with an infrared ray lamp. Itis noted that the conditions such as the rate of temperature elevation,substrate temperature, pressure, etc. are not limited to the above.

Next, a plume is generated by a laser ablation method in which a laserbeam is irradiated to a magnesium target for a buffer layer, therebypounding out magnesium atoms from the target. Then, this plume isirradiated toward the R-plane sapphire substrate 11, and brought incontact with the R-plane sapphire substrate 11, whereby a buffer layer12 composed of MgO with a cubic (100) orientation is formed by epitaxialgrowth on the R-plane sapphire substrate 11. A (100) plane of the bufferlayer 12 may preferably tilt with a [11-20] direction vector as arotation axis with respect to an R-plane (1-102) (hereafter also simplyreferred to as an “R-plane”) of the R-plane sapphire substrate 11. Thisis described with reference to FIG. 2 and FIG. 3.

FIG. 2 is a view schematically showing a hexagonal sapphire crystal, andFIG. 3 is a view schematically showing a tilt of the (100) plane of thebuffer layer 12. The R-plane (1-102) of the R-plane sapphire substrate11 corresponds to an N-S plane in FIG. 2. As shown in FIG. 3, withrespect to the N-S plane (in other words, the R-plane) of the R-planesapphire substrate 11, the (100) plane of the buffer layer 12 tilts withthe [11-20] direction vector as a rotation axis. In other words, alinear line defined at a crossing between the (100) plane of the bufferlayer 12 and the R-plane extends in parallel with the [11-20] directionvector. By forming such a buffer layer 12, a desired potassium niobatelayer 13 to be described below can be obtained. An angle δ definedbetween the (100) plane of the buffer layer 12 and the R-plane (1-102)of the R-plane sapphire substrate 11 may preferably be one degree orgreater but 15 degrees or smaller.

Also, by using MgO as the buffer layer 12, the dielectric property ofthe potassium niobate layer 13 may not be deteriorated even when Mg²⁺substitutes Nb⁵⁺ in the potassium niobate layer 13 and K(Mg, Nb)O₃ isgenerated.

The thickness of the buffer layer 12 is not particularly limited, butmay be 5 nm or greater but 100 nm or less, in view of preventing theR-plane sapphire substrate 11 and the potassium niobate layer 13 fromreacting each other, and preventing the potassium niobate layer 13 frombeing deteriorated due to the deliquescence of magnesium oxide itself.

As the method to pound out magnesium atoms or desired atoms from atarget in a later step, besides the method of irradiating a laser beamto a target surface described above, for example, a method ofirradiating (injecting) argon gas (inert gas) plasma or an electron beamto a target surface can also be used. However, the method of irradiatinga laser beam to a target surface is desirable among them. According tosuch a method, atoms can be readily and securely pounded out from atarget, with a vacuum apparatus having a simple structure equipped withan incident window of a laser beam.

The laser beam to be irradiated to a target may preferably be a pulsedbeam with a wavelength of about 150-300 nm, and a pulse length of about1-100 ns. More specifically, the laser beam may be, for example, anexcimer laser such as an ArF excimer laser, a KrF excimer laser, a XeClexcimer laser, or the like, a YAG laser, a YVO₄ laser, a CO₂ laser orthe like. Among the above, the ArF excimer laser and the KrF excimerlaser are particularly preferred. The ArF excimer laser and the KrFexcimer laser are easy to handle, and can effectively pound atoms from atarget.

Each of the conditions at the time of laser beam irradiation is notparticularly limited as long as the plume can sufficiently reach thesubstrate 11, and MgO as the buffer layer 12 can be epitaxially grown.The conditions at the time of laser beam irradiation may be as follows.For example, the energy density of the laser beam may preferably bebetween 2 J/cm² and 4 J/cm². The frequency of the laser beam maypreferably be between 5 Hz and 20 Hz. The distance between the targetand the substrate 11 (hereafter referred to as the “target-to-substratedistance”) may preferably be between 30 mm and 100 mm. The temperatureof the substrate may preferably be between 300° C. and 600° C. Thepartial pressure of oxygen during deposition may preferably be between1×10⁻⁵ Torr and 1×10⁻³ Torr.

(3) Next, as shown in FIG. 1, a potassium niobate layer 13 is formed bya laser ablation method on the buffer layer 12.

More specifically, a plume is generated by a laser ablation method inwhich a laser beam is irradiated to a target for the buffer layer, forexample, a K_(0.6)Nb_(0.4)O_(y) target, thereby pounding out potassium,niobium and oxygen atoms from this target. Then, the plume is irradiatedtoward the R-plane sapphire substrate 11, and brought in contact withthe buffer layer 12. As a result, a potassium niobate layer 13 in a(100) orientation in a pseudo cubic system expression is formed byepitaxial growth on the buffer layer 12. Further, as shown in FIG. 3,the (100) plane of the potassium niobate layer 13 tilts with a [11-20]direction vector as a rotation angle with respect to the R-plane (1-102)of the R-plane sapphire substrate 11. It is noted that FIG. 3 is adiagram schematically showing the tilt of the (100) plane of the bufferlayer 12, as described above, and is also a diagram schematicallyshowing the tilt of the (100) plane of the potassium niobate layer 13.

More concretely, the potassium niobate layer 13 may preferably include adomain that epitaxially grows in a b-axis orientation (which ishereafter also referred to as an “orthorhombic b-axis orientationdomain”), when a lattice constant of orthorhombic potassium niobate is2^(1/2) b<a<c, and a c-axis is a polarization axis. Also, the b-axis maypreferably tilt with a [11-20] direction vector as a rotation axis withrespect to the R-plane (1-102) of the R-plane sapphire substrate 11.When such a potassium niobate layer 13 is used, a surface acoustic waveelement 200 (see FIG. 19) with a high electromechanical couplingcoefficient can be obtained.

An angle Δ defined between the (100) plane of the potassium niobatelayer 13 and the R-plane (1-102) of the R-plane sapphire substrate 11may preferably be 1 degree or greater but 15 degrees or smaller. Moreconcretely, an angle defined between the b-axis of the orthorhombicpotassium niobate and the R-plane (1-102) of the R-plane sapphiresubstrate 11 may preferably be 1 degree or greater but 15 degrees orsmaller. It is noted that the angle Δ defined between the (100) plane ofthe potassium niobate layer 13 and the R-plane can be the same as ordifferent from the angle δ defined between the (100) plane of the bufferlayer 12 and the R-plane.

The conditions of the laser ablation method are not particularly limitedas long as the plume can sufficiently reach the buffer layer 12. Theconditions at the time of laser beam irradiation may be as follows. Forexample, the energy density of the laser beam may preferably be between2 J/cm² and 4 J/cm². The frequency of the laser beam may preferably bebetween 5 Hz and 20 Hz. The target-to-substrate distance may preferablybe between 30 mm and 100 mm. The temperature of the substrate maypreferably be between 600° C. and 800° C. The partial pressure of oxygenduring deposition may preferably be between 1×10⁻² Torr and 1 Torr.

In this embodiment, by selecting each of the conditions at the time oflaser ablation, pottasium niobate can be made to have a single crystalor polycrystal (preferably polycrystal in a single phase) structure.

In the above-described example, a K_(0.6)Nb_(0.4)O_(y) target is used.However, the composition ratio of the target is not limited to theabove. For example, for the formation of the potassium niobate layer 13,it is possible to use a target having a composition ratio that issuitable for conducting a Tri-Phase-Epitaxy method. Tri-Phase-Epitaxymethod is a method in which a vapor phase raw material is deposited on asubstrate that is maintained at temperatures in a solid-liquidcoexisting region, and a solid phase is precipitated from a liquidphase.

Concretely, a plume that is a raw material in a vapor phase is suppliedto a base substrate (which, in this embodiment, consists of thesubstrate 11 and the buffer layer 12) such that the mole compositionratio x of potassium in K_(x)Nb_(1-x)O_(y) in the state of a liquidphase immediately after being deposited on the base substrate is in therange of 0.5≦x≦x_(E). It is noted that x_(E) is a mole composition ratiox at an eutectic point of KNbO₃ and 3K₂O.Nb₂O₅ under a predeterminedoxygen partial pressure. Then, by maintaining the temperature T_(s) ofthe base substrate within the range of T_(E)≦T_(s)≦T_(m), the remainingliquid of K_(x)Nb_(1-x)O_(y) deposited on the base substrate suppliedfrom the plume is evaporated. By this, KNbO₃ single crystal can beprecipitated from K_(x)Nb_(1-x)O_(y) on the base substrate. It is notedthat T_(E) is a temperature at an eutectic point of KNbO₃ and 3K₂O.Nb₂O₅under a predetermined oxygen partial pressure. Also, T_(m) is a completemelting temperature under a predetermined oxygen partial pressure ofK_(x)Nb_(1-x)O_(y) in the state of a liquid phase immediately afterbeing deposited on the base substrate.

By the steps described above, the potassium niobate deposited body 100shown in FIG. 1 can be formed.

In addition, a polishing process to planarize the surface of thepotassium niobate layer 13 can be conducted if necessary. Buffpolishing, CMP (Chemical Mechanical Polishing) or the like can be usedas such a polishing process.

It is noted that, in the present embodiment, a laser ablation method isused as a film forming method for forming the buffer layer 12 and thepotassium niobate layer 13. However, the film forming method is notlimited to this, and, for example, a vapor deposition method, a MOCVDmethod, and a sputter method can be used.

1.3. According to the present embodiment, a buffer layer 12 composed ofMgO in a cubic (100) orientation is formed on a R-plane sapphiresubstrate 11, and a potassium niobate layer 13 is formed on the bufferlayer 12 by using a vapor phase method. By this, a single phase thinfilm of potassium niobate can be epitaxially grown in a b-axisorientation. By using the potassium niobate layer 13, a surface acousticwave element 200 (see FIG. 19) having a high electromechanical couplingcoefficient can be obtained, as described below.

Furthermore, in accordance with the present embodiment, a (100) plane ofthe potassium niobate layer 13 tilts with a [11-20] direction vector asa rotation angle with respect to an R-plane (1-102) of the R-planesapphire substrate 11. By using the potassium niobate layer 13, asurface acoustic wave element 200 having a higher electromechanicalcoupling coefficient can be obtained, as described below.

1.4. Experimental Examples

(1) First, a first experimental example is described. In the presentexperimental example, a potassium niobate deposited body 100 was formedaccording to a method described below. In the present experimentalexample, a thin film of polycrystal potassium niobate in a single phasecould be obtained.

First, a substrate 11 composed of an R-plane sapphire single crystalplate was degreased and washed through soaking the substrate 11 in anorganic solvent with an ultrasonic washing machine. As the organicsolvent, a 1:1 mixed solution of ethyl alcohol and acetone was used.After loading the substrate 11 onto a substrate holder, it wasintroduced together with the substrate holder in a vacuum apparatuswhose back pressure at room temperature was 1×10⁻⁸ Torr, oxygen gas wasintroduced such the oxygen partial pressure became 5×10⁻⁵ Torr, and thenthe substrate was heated to elevate its temperature up to 400° C. at arate of 20° C./minute with an infrared ray lamp.

Next, a pulsed beam of KrF excimer laser (with a wavelength of 248 nm)was injected in a surface of a magnesium target under conditions with anenergy density being 2.5 J/cm², a frequency being 10 Hz, and a pulselength being 10 ns, thereby generating a plasma plume of magnesium onthe target surface. The plasma plume was irradiated to the substrate 11under conditions with a substrate temperature being 400° C. and anoxygen partial pressure being 5×10 Torr, whereby a buffer layer 12consisting of MgO was formed. The target-to-substrate distance was 70mm, the irradiation time was 30 minutes, and the film thickness of thebuffer layer 12 was 10 nm.

Next, a pulsed beam of KrF excimer laser was injected in a surface of aK_(0.6)Nb_(0.4)O_(y) target under conditions with an energy densitybeing 3 J/cm², a frequency being 10 Hz, and a pulse length being 10 ns,thereby generating a plasma plume of K, Nb and O on the target surface.The plasma plume was irradiated to the substrate 11 under conditionswith a substrate temperature being 750° C. and an oxygen partialpressure being 1×10⁻¹ Torr, whereby a pottasium niobate layer 13 wasformed on the buffer layer 12. The target-to-substrate distance was 70mm, the irradiation time was 240 minutes, and the film thickness of thepotassium niobate layer 13 was of 1 μm.

By the steps described above, a potassium niobate deposited body 100(see FIG. 1) was obtained.

An X-ray diffraction pattern (2θ-θ scanning) of the potassium niobatelayer 13 obtained in the present experimental example is shown in FIG.4. All peaks shown in the X-ray diffraction pattern of FIG. 4 belong tosapphire and potassium niobate, and peaks belonging to other compoundsare not observed. Therefore, it was confirmed that the potassium niobateobtained in the present experimental example was a polycrystal but in asingle phase.

(2) Next, a second experimental example is described. In the presentexperimental example, a potassium niobate deposited body 100 was formedby the following method. In this experimental example, a thin film ofsingle crystal potassium niobate layer could be obtained.

First, a substrate 11 composed of an R-plane sapphire single crystalsubstrate was degreased and washed, in a similar manner as the firstexperimental example. Next, in a manner similar to the firstexperimental example, after loading the substrate 11 onto a substrateholder, it was introduced together with the substrate holder in a vacuumapparatus, oxygen gas was introduced, and then the substrate was heatedto elevate its temperature to 400° C. At this time, as shown in FIG. 5,in a pattern obtained by the reflection high speed electron beamdiffraction (Reflection High Energy Electron Diffraction (RHEED)) in asapphire [11-20] direction, kikuchi lines and strong reflection pointsthat are characteristic to a single crystal were observed.

Next, a pulsed beam of KrF excimer laser with a frequency being 20 Hzwas injected in a surface of a magnesium target, thereby generating aplasma plume of magnesium on the target surface. In this instance, theenergy density, pulse length, and wavelength were the same as those ofthe first experimental example, respectively. The plasma plume wasirradiated to the substrate 11, whereby a buffer layer consisting of MgOwas formed. In this instance, the substrate temperature, oxygen partialpressure, target-to-substrate distance, irradiation time, film thicknesswere the same as those of the first experimental example, respectively.

A RHEED pattern in a sapphire [11-20] direction of the deposited bodythus obtained was investigated, and a pattern shown in FIG. 6 wasobtained. A diffraction pattern appears in this RHEED pattern, and itwas confirmed that the buffer layer 12 composed of MgO epitaxially grew.

Further, an X-ray diffraction pattern (2θ-θ scanning) of the bufferlayer 12 composed of MgO in the deposited body is shown in FIG. 7. Asshown in FIG. 7, no peak other than the peaks of the substrate 11 wasobserved. X-ray diffraction patterns (ω scanning) obtained when thevalue 2θ was fixed at MgO (200) (2θ=42.92° when a=0.4212 nm) are shownin FIG. 8 and FIG. 9. When the rotation axis of the ω scanning was inparallel with the sapphire [11-20], a peak shifted by 9.2° from thecenter was observed as shown in FIG. 8. When the rotation axis of the ωscanning was in parallel with the sapphire [−1101], no peak wasobserved, as shown in FIG. 9. Based on these results, it was confirmedthat an MgO (100) film tilted by about 9° from the substrate 11epitaxially grew.

Next, a pulsed beam of KrF excimer laser was injected in a surface of aK_(0.67)Nb_(0.33)O_(y) target under conditions with an energy densitybeing 2 J/cm², thereby generating a plasma plume of K, Nb and O on thetarget surface. In this instance, the frequency and pulse length werethe same as those of the first experimental example. The plasma plumewas irradiated to the substrate 11 under conditions with a substratetemperature being 600° C. and an oxygen partial pressure being 1×10⁻²Torr, whereby a pottasium niobate layer 13 was formed on the bufferlayer 12. The film thickness of the potassium niobate layer 13 was 0.5μm. Also, the target-to-substrate distance, and irradiation time werethe same as those of the first experimental example.

By the steps described above, a potassium niobate deposited body 100(see FIG. 1) was obtained.

A RHEED pattern in a sapphire [11-20] direction of the deposited bodythus obtained was investigated, and a pattern shown in FIG. 10 wasobtained. A clear diffraction pattern appears in this RHEED pattern, andit was confirmed that the potassium niobate epitaxially grew.

Further, an X-ray diffraction pattern (2θ-θ scanning) of the potassiumniobate (KNbO₃) layer 13 of the deposited body is shown in FIG. 11. Asshown in FIG. 11, peaks of KNbO₃ (100)_(pc), and KNbO₃ (200)_(pc) wereobserved, as KNbO₃ is expressed by plane index of pseudo cubic.Accordingly, it was confirmed that KNbO₃ was (100)_(pc) oriented. X-raydiffraction patterns (ω scanning) of KNbO₃ (200)_(pc) (2θ=45.12°) areshown in FIG. 12 and FIG. 13. When the rotation axis of the ω scanningwas in parallel with the sapphire [11-20], a peak shifted by 6.3° fromthe center was observed as shown in FIG. 12. When the rotation axis ofthe ω scanning was in parallel with the sapphire [−1101], no peak wasobserved, as shown in FIG. 13. Based on these results, it was confirmedthat a KNbO₃ (100)_(pc) film tilted by about 6° from the substrate 11grew.

Moreover, when X-ray diffraction pole figures were investigated, theresults shown in FIG. 14-FIG. 16 were obtained. FIG. 14, FIG. 15 andFIG. 16 are X-ray diffraction pole figures of sapphire (0006)(2θ=41.7°), MgO (202) (2θ=62.3°), and KNbO₃ (101)_(pc) (2θ=31.5°),respectively. As shown in FIG. 15 and FIG. 16, spots of MgO (202) andKNbO₃ (101)_(pc) both indicate symmetry four times, and it was foundthat orientations of epitaxial growth are in relation of KNbO₃(100)_(pc)/MgO (100)/sapphire (1-102) in inter-plane, and KNbO₃[010]_(pc)//MgO [010]//sapphire [11-20] in in-plane. Also, as shown inFIG. 15 and FIG. 16, the centers of these four spots are shifted fromthe center of the pole figure (Psi=0 degree) in the sapphire [−1101]direction by about 9 degrees and about 6 degrees, respectively. Theycoincide with the shift amounts in the ω scanning described above.Accordingly, it was confirmed that the buffer layer 12 composed of MgOepitaxially grew with its (100) plane tilted with a [11-20] directionvector as a rotation axis by about 9 degrees with respect to the R-planeof the substrate 11, and the potassium niobate layer 13 epitaxially grewwith its (100) plane in a pseudo cubic expression tilted with a [11-20]direction vector as a rotation axis by about 6 degrees with respect tothe R-plane of the substrate 11.

Also, Raman scattering spectra were measured, and results shown in FIG.17 and FIG. 18 were obtained. FIG. 17 and FIG. 18 correspond to thegeometry of z (x, x)−z, and x (x, y)−z, respectively. The formulaindicating the geometry means “the direction of momentum of incidentlight (polarization direction of incident light, polarization directionof scattering light)—the direction of momentum of scattering light.” Inthe geometry of z (x, x)−z, as shown in FIG. 17, peaks of the A₁vibration mode near 280 cm⁻¹ and 600 cm⁻¹ are strongly observed, butpeaks of the B₁ vibration mode near 250 cm⁻¹ and 530 cm⁻¹ are hardlyobserved. On the other hand, in the geometry of z (x, y)−z, as shown inFIG. 18, peaks of the B₁ vibration mode near 250 cm⁻¹ and 530 cm⁻¹ arestrongly observed, but peaks of the A₁ vibration mode near 280 cm⁻¹ and600 cm⁻¹ are hardly observed. In other words, the peak intensities ofthe A₁ vibration mode and the B₁ vibration mode are reversed between thecase of the geometry of z (x, y)−z, and the case of the geometry of z(x, x)−z.

From these results, a consideration was made as to which one of domainsthat can be obtained in a pseudo cubic (100) orientation, namely, anorthorhombic (101) domain or an orthorhombic (010) domain (orthorhombicb-axis orientation domain), is predominant. Table 1 shows selectionrules of phonon mode which are observed in Raman scattering spectraobtained for the respective domain structures based on the space groups.It is noted that “O” in Table 1 indicates being observable, and “N”indicates being unobservable.

TABLE 1 Domain Geometric B₁(T0) A₁(T0) A₂ B₁(T0) A₁(T0) A₁(L0) StructureCondition 249 cm⁻¹ 281.5 cm⁻¹ 282 cm⁻¹ 534 cm⁻¹ 606.5 cm⁻¹ 834 cm⁻¹(010) z(x, x) − z N O N N O N Domain z(x, y) − z O N N O N N (101) z(x,x) − z O O O O O O Domain z(x, y) − z O O O O O O

When the polarization plane of incident light and the polarization planeof scattering light are set in parallel with each other or orthogonal toeach other, the polarization axis becomes to be in parallel with ororthogonal to the electric field of the incident light, respectively, inthe case of the (010) domain, and therefore one of the A₁ and B₁ modesis selectively observed. On the other hand, in the case of the (101)domain, the polarization axis is positioned twisted with respect to theelectric field of the incident light, and therefore both of the A₁ andB₁ modes are observed together without regard to the orientation of thepolarization plane. Accordingly, the results shown in FIG. 17 and FIG.18 coincide with the selection rules of the peaks obtained based on theassumption that the (010) domain (orthorhombic b-axis orientationdomain) is predominant, and this indicates that the obtained potassiumniobate layer 13 is composed of an orthorhombic b-axis orientationdomain.

Furthermore, based on the results of measurement of Raman scatteringspectra, and the results of measurement of X-ray diffractions describedabove, it was confirmed that the b-axis of orthorhombic potassiumniobate tilts, with a [11-20] direction vector as a rotation axis, withrespect to the R-plane of the substrate 11.

2. Second Embodiment

2.1. Next, an example of a surface acoustic wave element in accordancewith a second embodiment of the invention is described with reference tothe accompanying drawings. FIG. 19 is a cross-sectional viewschematically showing a surface acoustic wave element 200 in accordancewith the present embodiment. In FIG. 19, members that are substantiallythe same as the members of the potassium niobate deposited body 100shown in FIG. 1 are appended with the same reference numbers, and theirdetailed description is omitted.

The surface acoustic wave element 200 includes a substrate 11, a bufferlayer 12 formed on the substrate 11, a pottasium niobate layer 13 formedon the buffer layer 12, and inter-digital transducers (hereafter,referred to as “IDT electrodes”) 18 and 19 formed on the potassiumniobate layer 13. The IDT electrodes 18 and 19 have predeterminedpatterns.

The surface acoustic wave element 200 in accordance with the presentembodiment includes a potassium niobate deposited body in accordancewith an embodiment of the invention, for example, the potassium niobatedeposited body 100 shown in FIG. 1. Accordingly, the potassium niobatelayer 13 composing the surface acoustic wave element 200 has the samecharacteristics as those of the potassium niobate layer 13 of thepotassium niobate deposited body 100. The potassium niobate layer 13 iscomposed of single crystal or polycrystal potassium niobate, asdescribed above.

2.2. The surface acoustic wave element 200 in accordance with thepresent embodiment is formed with a potassium niobate deposited body inaccordance with the embodiment of the invention, for example, in thefollowing manner.

First, a metal layer is formed by a vacuum vapor deposition method onthe pottasium niobate layer 13 of the pottasium niobate deposited body100 shown in FIG. 1. As the metal layer, for example, aluminum can beused. Next, the metal layer is patterned by using known lithography andetching techniques, to thereby form IDT electrodes 18 and 19 on thepottasium niobate layer 13.

2.3. The surface acoustic wave element in accordance with the presentembodiment has a potassium niobate deposited body in accordance with anembodiment of the invention. Therefore, in accordance with the presentembodiment, a surface acoustic wave element having a highelectromechanical coupling coefficient can be achieved.

2.4. Next, an example of experiments conducted on the surface acousticwave element 200 in accordance with the present embodiment is describedbelow.

(1) A surface acoustic wave element 200 in accordance with a firstexperimental example was formed by using the potassium niobate depositedbody 100 of the first experimental example in accordance with the firstembodiment described above. The potassium niobate deposited body 100 hada polycrystal potassium niobate layer 13 in a single phase. It is notedthat, as the IDT electrodes, aluminum layers of 100 nm in thickness wereused. L & S (Line and Space) of the IDT electrodes was 1.25 μm.

The propagation speed V_(open) of surface acoustic wave between the IDTelectrodes 18 and 19 was measured with the obtained surface acousticwave element 200. An acoustic velocity obtained based on the measurementresults was 5000 m/s. Also, an electromechanical coupling coefficientobtained based on a difference between the above and the propagationspeed V_(short) of surface acoustic wave when an area between the IDTelectrodes 18 and 19 was covered by a metal thin film was 10%.

Also, a surface acoustic wave element 200 using potassium sodium niobatetantalate solid solution (K_(1-x)Na_(x)Nb_(1-y)Ta_(y)O₃ (0<x<1, 0<y<1))instead of potassium niobate (KNbO₃) provided similar effects.

(2) A surface acoustic wave element 200 in accordance with a secondexperimental example was formed by using the potassium niobate depositedbody 100 of the second experimental example in accordance with the firstembodiment described above. The potassium niobate deposited body 100 hada single crystal potassium niobate layer 13. The potassium niobate layerincludes an orthorhombic b-axis orientation domain, and the b-axistitles, with a [11-20] direction vector as a rotation axis, with respectto the R-plane of the substrate 11. It is noted that, like the firstexperimental example, as the IDT electrodes, aluminum layers of 100 nmin thickness were used.

The propagation speed V_(open) of surface acoustic wave between the IDTelectrodes 18 and 19 was measured with the obtained surface acousticwave element 200. An acoustic velocity obtained based on the measurementresults was 5000 m/s. Also, an electromechanical coupling coefficientobtained based on a difference between the above and the propagationspeed V_(short) of surface acoustic wave when an area between the IDTelectrodes 18 and 19 was covered by a metal thin film was 35%. Ascompared to the electromechanical coupling coefficient (10%) obtainedwhen the polycrystal potassium niobate layer 13 was used (in the case ofthe first experimental example), it became clear that theelectromechanical coupling coefficient improved when the single crystalpotassium niobate layer 13 was epitaxially grown with its b-axis tilted.

3. Third Embodiment

3.1. Next, an example of a frequency filter in accordance with a thirdembodiment of the invention is described with reference to theaccompanying drawings. FIG. 20 is a view schematically showing afrequency filter in accordance with the present embodiment.

As shown in FIG. 20, the frequency filter has a base substrate 140. Apotassium niobate deposited body in accordance with an embodiment of theinvention, for example, the potassium niobate deposited body 100 shownin FIG. 1 may be used as the base substrate 140.

IDT electrodes 141 and 142 are formed on an upper surface of the basesubstrate 140. Also, acoustic absorber sections 143 and 144 are formedon the upper surface of the base substrate 140 in a manner to interposethe IDT electrodes 141 and 142. The acoustic absorber sections 143 and144 absorb surface acoustic waves that propagate over the surface of thebase substrate 140. A high frequency signal source 145 is connected tothe IDT electrode 141 formed on the base substrate 140, and a signalline is connected to the IDT electrode 142.

3.2. Next, operations of the frequency filter described above aredescribed.

When a high frequency signal is outputted from the high frequency signalsource 145 in the above-described structure, the high frequency signalis impressed to the IDT electrode 141, whereby a surface acoustic waveis generated on the upper surface of the base substrate 140. The surfaceacoustic waves propagating from the IDT electrode 141 toward the soundabsorbing portion 143 are absorbed by the sound absorbing portion 143.However, among the surface acoustic waves propagating toward the IDTelectrode 142, only those surface acoustic waves with a specificfrequency or specific band frequency determined according to the pitchand the like of the IDT electrode 142 are converted to electric signals,and outputted to terminals 146 a and 146 b via the signal line. It isnoted that the majority of frequency components other than theaforementioned specific frequency or specific band frequency is absorbedby the sound absorbing portion 144 after passing through the IDTelectrode 142. In this way, of the electric signals supplied to the IDTelectrode 141 provided in the frequency filter of the presentembodiment, it is possible to obtain (filter) only surface acousticwaves of a specific frequency or specific band frequency.

4. Fourth Embodiment

4.1. Next, an oscillator in accordance with a fourth embodiment of theinvention is described with reference to the accompanying drawings. FIG.21 is a view schematically showing an oscillator in accordance with thepresent embodiment.

As shown in FIG. 21, the oscillator has a base substrate 150. As thebase substrate 150, a potassium niobate deposited body in accordancewith an embodiment of the invention, for example, the potassium niobatedeposited body 100 shown in FIG. 1 may be used, like the frequencyfilter described above.

An IDT electrode 151 is formed on an upper surface of the base substrate150, and IDT electrodes 152 and 153 are formed in a manner to interposethe IDT electrode 151. A high frequency signal source 154 is connectedto one of comb teeth-shaped electrodes 151 a which form the IDTelectrode 151, while a signal line is connected to the other combteeth-shaped electrode 151 b. It is noted that the IDT electrode 151corresponds to an electric signal application electrode, and the IDTelectrodes 152 and 153 correspond to resonating electrodes forresonating a specific frequency component or a specific band frequencycomponent of the surface acoustic waves generated by the IDT electrode151.

4.2. Next, operations of the oscillator described above are described.

When a high frequency signal is outputted from the high frequency signalsource 154 in the above-described structure, this high frequency signalis impressed on one of the comb teeth-shaped electrodes 151 a of the IDTelectrode 151. As a result, surface acoustic waves that propagate towardthe IDT electrode 152 and surface acoustic waves that propagate towardthe IDT electrode 153 are generated on the upper surface of the basesubstrate 150. Of these surface acoustic waves, those surface acousticwaves of a specific frequency component are reflected at the IDTelectrode 152 and the IDT electrode 153, and a standing wave isgenerated between the IDT electrode 152 and the IDT electrode 153. Thesurface acoustic wave with this specific frequency component isrepeatedly reflected at the IDT electrode 152 and the IDT electrode 153.As a result, specific frequency components or specific band frequencycomponents are resonated and the amplitude increases. A portion of thesurface acoustic waves of the specific frequency component or thespecific band frequency component are extracted from the other combteeth-shaped electrode 151 b of the IDT electrode 151, and the electricsignal of the frequency (or the frequency having a certain band)corresponding to the resonance frequency between the IDT electrode 152and the IDT electrode 153 can be extracted at terminals 155 a and 155 b.

4.3. FIG. 22 and FIG. 23 are views schematically showing an example inwhich the oscillator described above is applied as a VCSO (VoltageControlled SAW Oscillator). FIG. 22 is a cut-out side view, and FIG. 23is a cut-out plan view.

The VCSO is housed inside a metallic (aluminum or stainless) box 60. AnIC (integrated circuit) 62 and an oscillator 63 are mounted on asubstrate 61. In this case, the IC 62 controls the frequency to beapplied to the oscillator 63 in response to the voltage inputted from anexternal circuit (not shown).

The oscillator 63 includes IDT electrodes 65 a, 65 b and 65 c formed ona base substrate 64. Its structure is generally the same as that of theoscillator shown in FIG. 21. As the base substrate 64, like theoscillator described above and shown in FIG. 21, a potassium niobatedeposited body in accordance with an embodiment of the invention, forexample, the potassium niobate deposited body 100 shown in FIG. 1 may beused.

A wiring 66 for electrically connecting the IC 62 and the oscillator 63is patterned on the substrate 61. For example, the IC 62 and the wiring66 are connected by a wire line 67 such as a gold line, and theoscillator 63 and the wiring 66 are connected by a wire line 68 such asa gold line, whereby the IC 62 and oscillator 63 are electricallyconnected to each other through the wiring 66.

The VCSO shown in FIG. 22 and FIG. 23 can be employed as a VCO (VoltageControlled Oscillator) for a PLL circuit shown in FIG. 24, for example.FIG. 24 is a block diagram showing the basic structure of a PLL circuit.The PLL circuit is formed from a phase comparator 71, a low band filter72, an amplifier 73 and a VCO 74. The phase comparator 71 compares thephases (or frequencies) of signals inputted from an input terminal 70and outputted from the VCO 74, and outputs an error voltage signal, thevalue of which is set according to the difference between these signals.The low band filter 72 transmits only the low frequency components atthe position of the error voltage signal outputted from the phasecomparator 71. The amplifier 73 amplifies the signal outputted from thelow band filter 72. The VCO 74 is an oscillator circuit in which theoscillation frequency oscillating according to the voltage valueinputted is continuously changed within a certain range.

The PLL circuit having such a structure operates so as to decrease thedifference between the phases (or frequencies) inputted from the inputterminal 70 and outputted from the VCO 74, and synchronizes thefrequency of the signal outputted from the VCO 74 with the frequency ofthe signal inputted from the input terminal 70. When the frequency ofthe signal outputted from the VCO 74 and the frequency of the signalinputted from the input terminal 70 are synchronized with each other,the PLL circuit outputs a signal that matches with the signal inputtedfrom the input terminal 70 after excluding a specific phase difference,and conforms to the changes in the input signal.

As described above, frequency filters and oscillators in accordance withthe embodiment of the invention have surface acoustic wave elementshaving a high electromechanical coupling coefficient in accordance withthe embodiment of the invention. Therefore, in accordance with thepresent embodiment, miniaturization of frequency filters and oscillatorscan be realized.

5. Fifth Embodiment

5.1. Next, first examples of an electronic circuit and an electronicapparatus in accordance with a fifth embodiment of the invention aredescribed with reference to the accompanying drawings. FIG. 25 is ablock diagram showing an electrical structure of an electronic circuit300 in accordance with the embodiment. It is noted that the electronicapparatus 300 may be, for example, a cellular phone.

The electronic apparatus 300 has an electronic circuit 310, atransmitter 80, a receiver 91, an input section 94, a display section95, and an antenna section 86. The electronic circuit 310 has atransmission signal processing circuit 81, a transmission mixer 82, atransmission filter 83, a transmission power amplifier 84, a transceiverwave divider 85, a low noise amplifier 87, a reception filter 88, areception mixer 89, a reception signal processing circuit 90, afrequency synthesizer 92, and a control circuit 93.

In the electronic circuit 310, the frequency filters shown in FIG. 20can be used as the transmission filter 83 and the reception filter 88.The frequency that is filtered (i.e., the frequency which is permittedto pass through the filter) is set separately at the transmission filter83 and the reception filter 88 according to the required frequency inthe signal outputted from the transmission mixer 82 and the requiredfrequency at the reception mixer 89. As the VCO 74 of the PLL circuit(see FIG. 24) that is provided within the frequency synthesizer 92, theoscillator shown in FIG. 21 or the VCSO shown in FIGS. 22 and 23 can beused.

The transmitter 80 can be realized, for example, with a microphone whichconverts sound wave signals into electric signals. The transmissionsignal processing circuit 81 is a circuit for performing such processingas D/A conversion, modulation, etc. on the electric signal to beoutputted from the transmitter 80. The transmission mixer 82 mixes thesignal outputted from the transmission signal processing circuit 81using the signal outputted from the frequency synthesizer 92. Thetransmission filter 83 permits passage of only those signals of therequired frequency from among the intermediate frequencies (hereafterreferred to as “IF”), and cuts unnecessary frequency signals. The signaloutputted from the transmission filter 83 is converted to an RF signalby a converting circuit (not shown). The transmission power amplifier 84amplifies the power of the RF signal outputted from the transmissionfilter 83 and outputs this amplified result to the transceiver wavedivider 85.

The transceiver wave divider 85 transmits the RF signal that isoutputted from the transmission power amplifier 84 through the antennasection 86 in the form of radio waves. Also, the transceiver wavedivider 85 divides the reception signal received by the antenna 86, andoutputs the result to the low noise amplifier 87. The low noiseamplifier 87 amplifies the reception signal from the transceiver wavedivider 85. It is noted that the signal outputted from the low noiseamplifier 87 is converted to IF by a converting circuit (not shown).

The reception filter 88 permits passage of only those signals of therequired frequency from among the IF that were converted by a convertingcircuit (not shown), and cuts unnecessary frequency signals. Thereception mixer 89 uses the signal outputted from the frequencysynthesizer 92 to mix the signals outputted from the reception filter88. The reception signal processing circuit 90 performs such processingas A/D conversion, demodulation, etc., to the signal outputted from thereception mixer 89. The receiver 91 is realized with, for example, asmall speaker or the like which converts electrical signals into soundwaves.

The frequency synthesizer 92 is a circuit that generates the signal tobe supplied to the transmission mixer 82 and the signal to be suppliedto the reception mixer 89. The frequency synthesizer 92 is equipped witha PLL circuit. The frequency synthesizer 92 divides the signal outputtedfrom this PLL circuit and can generate a different signal. The controlcircuit 93 controls the transmission signal processing circuit 81, thereception signal processing circuit 90, the frequency synthesizer 92,the input section 94, and the display section 95. The display section 95displays, for example, the device status to the user of the cellularphone. The input section 94 is provided, for example, for the user ofthe cellular phone to input directions.

5.2. Next, second examples of an electronic circuit and an electronicapparatus in accordance with the fifth embodiment of the invention aredescribed with reference to the accompanying drawings. In the presentembodiment, a reader/writer 2000 and a communications system 3000 usingthe same are described as examples of an electronic apparatus. FIG. 26is a view showing the communications system 3000 that uses thereader/writer 2000 in accordance with the present embodiment, and FIG.27 is a schematic block diagram of the communications system 3000 shownin FIG. 26.

As shown in FIG. 26, the communications system 3000 includes thereader/writer 2000 and a contactless information medium 2200. Thereader/writer 2000 transmits a radio wave W (hereafter also referred toas a “career”) having a carrier frequency f_(c) to the contactlessinformation medium 2200 or receives the same from the contactlessinformation medium 2200, to thereby communicate with the contactlessinformation medium 2200 by using radio communications. The radio wave Wcan use any carrier frequency fc in an arbitrary frequency band. Asshown in FIG. 26 and FIG. 27, the reader/writer 2000 has a main body2105, an antenna section 2110 located on the top surface of the mainbody 2105, a control interface section 2120 stored in the main body2105, and a power supply circuit 172. The antenna section 2110 and thecontrol interface section 2120 are electrically connected to each otherby a cable 2180. Further, although not shown, the reader/writer 2000 isconnected to an external host apparatus (processor apparatus, etc.)through the control interface section 2120.

The antenna section 2110 has a function to communicate information withthe contactless information medium 2200. The antenna section 2110 has aprescribed communication area (area shown by a dotted line), as shown inFIG. 26. The antenna section 2110 is composed of a loop antenna 112 anda matching circuit 114.

The control interface section 2120 includes a transmission section 161,a damping oscillation cancellation section (hereafter, referred to as a“cancellation section”) 165, a reception section 168, and a controller160.

The transmission section 161 modulates data transmitted from an externalunit (not shown), and transmits the same to a loop antenna 112. Thetransmission section 161 has an oscillation circuit 162, a modulationcircuit 163, and a driving circuit 164. The oscillation circuit 162 is acircuit for generating a carrier with a predetermined frequency. Theoscillation circuit 162 is usually formed with a quartz oscillator orthe like. By using the oscillator in accordance with the embodimentdescribed above, its communication frequency can be improved to a higherfrequency and its detection sensitivity can be improved. The modulationcircuit 163 is a circuit that modulates the carrier according toinformation given. The driving circuit 164 receives the modulatedcareer, amplifies its electric power, and drives the antenna section2110.

The cancellation section 165 has a function to control a dampedoscillation generated by the loop antenna 112 of the antenna section2110 which occurs with ON/OFF of the career. The cancellation section165 includes a logic circuit 166 and a cancellation circuit 167.

The reception section 168 includes a detection section 169 and ademodulator circuit 170. The reception section 168 demodulates a signalthat is transmitted from the contactless information medium 2200. Thedetection section 169 detects a change in the current that circulates inthe loop antenna 112. The detection section 169 may include, forexample, an RF filter. As the RF filter, a quartz oscillator or the likemay be used. By using the frequency filter in accordance with theembodiment described above, the communication frequency can be improvedto a higher frequency, the detection sensitivity can be improved, andminiaturization becomes possible. The demodulator circuit 170demodulates the changed portion detected by the detection section 169.

The controller 160 retrieves information from the demodulated signal,and transfers the same to an external device. The power supply circuit172 receives the supply of an electric power from outside, appropriatelyconverts the voltage, and supplies a necessary electric power to eachcircuit. It is noted that a built-in battery may be used as the powersource.

The contactless information medium 2200 communicates with thereader/writer 2000 by using electromagnetic waves (radio waves). As thecontactless information medium 2200, for example, a contactless IC tag,a contactless IC card or the like can be enumerated.

Next, operations of the communication system 3000 that uses thereader/writer 2000 in accordance with the present embodiment aredescribed. When data is sent to the contactless information medium 2200from the reader/writer 2000, if the data is sent from an external device(not shown), the data is processed by the controller 160 in thereader/writer 2000 and sent to the transmission section 161. In thetransmission section 161, a high frequency signal of constant amplitudeis supplied from the oscillation circuit 162 as a career, the career ismodulated by the modulation circuit 163, and a modulated high frequencysignal is outputted. The modulated high frequency signal outputted fromthe modulation circuit 163 is supplied to the antenna section 2110through the driving circuit 164. At the same time, the cancellationsection 165 generates a predetermined pulse signal in synchronism withan OFF timing of the modulated high frequency signal, to therebycontribute to the control of the damping oscillation in the loop antenna112.

In the contactless information medium 2200, the modulated high frequencysignal is supplied through an antenna section 186 to a reception circuit180. Also, the modulated high frequency signal is supplied to a powersupply circuit 182, and a predetermined power supply voltage necessaryfor each section of the contactless information medium 2200 isgenerated. The data outputted from the reception circuit 180 isdemodulated and supplied to a logic control circuit 184. The logiccontrol circuit 184 operates based on the output of a clock 183,processes the supplied data, and writes certain data in a memory 185.

When data is sent from the contactless information medium 2200 to thereader/writer 2000, the following operations take place. In thereader/writer 2000, a high frequency signal of constant amplitude isoutputted from the modulation circuit 163 without being modulated. Thehigh frequency signal is sent to the contactless information medium 2200through the driving circuit 164 and the loop antenna 112 of the antennasection 2110.

In the contactless information medium 2200, data read from the memory185 is processed by the logic control circuit 184, and supplied to atransmission circuit 181. The transmission circuit 181 may have aswitch, wherein the switch turns ON and OFF according to “1” and “0” bitof the data.

In the reader/writer 2000, when the switch of the transmission circuit181 turns ON and OFF, the load on the loop antenna 112 of the antennasection 2110 changes. Therefore, the amplitude of the high frequencycurrent that circulates in the loop antenna 112 changes. In other words,the high frequency current is amplitude-modulated by the data suppliedfrom the contactless information medium 2200. The high frequency currentis detected by the detection section 169 of the reception section 168,and demodulated by the demodulation circuit 170 whereby data isobtained. The data is processed by the controller 160, and transmittedto an external apparatus or the like.

5.3. Electronic circuits and electronic apparatuses in accordance withthe embodiment of the invention have surface acoustic wave elementshaving a high electromechanical coupling coefficient in accordance withthe embodiment of the invention. Therefore, in accordance with thepresent embodiment, power saving of electronic circuits and electronicapparatuses can be achieved.

The embodiments of the invention are described above in detail. However,those skilled in the art should readily understand that manymodifications can be made without substantially departing from the novelmatter and effects of the invention. Accordingly, all of such modifiedexamples are also included in the scope of the invention.

For example, frequency filters and oscillators in accordance with theembodiments of the invention are also applicable to wide-band filtersand VCOs in UWB systems, cellular phones, and wireless LAN.

Although the surface acoustic wave element, frequency filter, frequencyoscillator, electronic circuit, electronic equipment, and reader/writerin accordance with the embodiments of the present invention aredescribed above, the present invention can be freely modified within thescope of the present invention without being limited to the embodimentsdescribed above.

For example, in the embodiments described above, a cellular phone and acommunications system using a reader/writer device are described asexamples of electronic apparatuses, and electronic circuits installed inthe cellular phone and the reader/writer device are described asexamples of electronic circuits. However, the invention is not limitedto those described above, and is applicable to various mobiletelecommunications equipment and electronic circuits installed therein.For example, the invention is also applicable to floor typetelecommunications equipment such as tuners that receive BS (BroadcastSatellite) broadcasting and electronic circuits installed therein, andalso applicable to electronic equipment such as HUB or the like that useoptical signals that propagate in optical cables and electronic circuitsinstalled therein.

1. A potassium niobate deposited body comprising: an R-plane sapphiresubstrate; and a potassium niobate layer or a potassium niobate solidsolution layer formed above the R-plane sapphire substrate, wherein thepotassium niobate layer or the potassium niobate solid solution layerepitaxially grows in a (100) orientation in a pseudo cubic systemexpression, and the potassium niobate layer or the potassium niobatesolid solution layer has a (100) plane that tilts with a [11-20]direction vector as a rotation axis with respect to an R-plane (1-102)of the R-plane sapphire substrate.
 2. A potassium niobate deposited bodyaccording to claim 1, wherein an angle defined between the (100) planeof the potassium niobate layer or the potassium niobate solid solutionlayer and the R-plane (1-102) of the R-plane sapphire substrate is onedegree or greater but 15 degrees or smaller.
 3. A potassium niobatedeposited body according to claim 1, wherein the potassium niobate layerincludes a domain that epitaxially grows in a b-axis orientation, when alattice constant of orthorhombic potassium niobate is 2^(1/2)b<a<c, anda c-axis is a polarization axis, and the b-axis tilts with a [11-20]direction vector as a rotation axis with respect to the R-plane (1-102)of the R-plane sapphire substrate.
 4. A potassium niobate deposited bodyaccording to claim 3, wherein an angle defined between the b-axis andthe R-plane (1-102) of the R-plane sapphire substrate is one degree orgreater but 15 degrees or smaller.
 5. A potassium niobate deposited bodyaccording to claim 1, wherein the potassium niobate solid solution layerconsists of a solid solution that is expressed byK_(1−x)Na_(x)Nb_(1−y)Ta_(y)O₃ (0<x<1, 0<y<1).
 6. A potassium niobatedeposited body according to claim 1, comprising a buffer layer formedabove the R-plane sapphire substrate, wherein the potassium niobatelayer or the potassium niobate solid solution layer is formed above thebuffer layer.
 7. A potassium niobate deposited body according to claim6, wherein the buffer layer epitaxially grows in a cubic (100)orientation, and a (100) plane of the buffer layer tilts with a [11-20]direction vector as a rotation axis with respect to the R-plane (1-102)of the R-plane sapphire substrate.
 8. A potassium niobate deposited bodyaccording to claim 7, wherein an angle defined between the (100) planeof the buffer layer and the R-plane (1-102) of the R-plane sapphiresubstrate is one degree or greater but 15 degrees or smaller.
 9. Apotassium niobate deposited body according to claim 6, wherein thebuffer layer consists of a metal oxide having a rock salt structure. 10.A potassium niobate deposited body according to claim 9, wherein themetal oxide is magnesium oxide.
 11. A surface acoustic wave elementcomprising the potassium niobate deposited body according to claim 1.12. A frequency filter comprising the surface acoustic wave elementaccording to claim
 11. 13. An electronic circuit comprising thefrequency filter according to claim
 12. 14. An electronic apparatuscomprising the electronic circuit according to claim
 13. 15. Anoscillator comprising the surface acoustic wave element according toclaim
 11. 16. An electronic circuit comprising the oscillator accordingto claim
 15. 17. An electronic apparatus comprising the electroniccircuit according to claim
 16. 18. A potassium niobate deposited bodycomprising: an R-plane sapphire substrate; a buffer layer formed abovethe R-plane sapphire substrate; and a potassium niobate layer or apotassium niobate solid solution layer formed above the buffer layer,wherein the buffer layer epitaxially grows in a cubic (100) orientation,and a (100) plane of the buffer layer tilts with a [11-20] directionvector as a rotation axis with respect to an R-plane (1-102) of theR-plane sapphire substrate.
 19. A method for manufacturing a potassiumniobate deposited body comprising: forming above an R-plane sapphiresubstrate a potassium niobate layer or a potassium niobate solidsolution layer that epitaxially grows in a (100) orientation in a pseudocubic system expression, wherein a (100) plane of the potassium niobatelayer or the potassium niobate solid solution layer is formed to tiltwith a [11-20] direction vector as a rotation axis with respect to anR-plane (1-102) of the R-plane sapphire substrate.